Hot wire electromagnetic flasher



Jan. 11, 1966 J CREAGER 3,229,126

HOT WIRE ELECTROMAGNETIC FLASHER Filed June 8, 1961 IN V EN TOR.

ATT NEY United States Patent 1 3,229,126 HOT WIRE ELECTROMAGNETIC FLASHER John E. Creager, Mount Morris, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed June 8, 1961, Ser. No. 115,758 Claims. (Cl. 307132) This invention relates to a thermoresponsive electric flasher, andparticularly to a flasher of the type used in warning signal circuits on vehicles.

a It is well known to utilize a heat expansible wire to operate switching contacts within a flasher and also to use a relay actuated by those contacts. Frequently, however, it is found that the contacts within a flasher become defective due to excessive arcing and that a flasher is insensitive to major load changes or, on the other hand, is unduly sensitive to minor load changes.

An object of this invention is to provide a flasher arrangement whereby arcing between contacts is reduced, and further to provide a flasher which will give a positive indication of a drop in load large enough to be caused by failure of a load element, and yet be unaffected in operation by smaller load changes.

The invention is carried out by providing a relay conneeted with one terminal of a voltage source and means for alternately connecting the coil to the other terminal of the voltage source and shunting out the coil.

Another aspect of the invention provides a heat expansible wire which is connected across a voltage source during periods of heating the wire and disconnected from the source during periods of cooling.

The above and other advantages will be made more apparent from the following specification taken in conjunction with the accompanying drawings wherein like numerals refer to like parts, and wherein:

FIGURE 1 is a schematic electrical diagram of a flasher in a lighting system according to the invention;

FIGURE 2 is a front elevational view of a flasher according to the invention with parts broken away and in section;

4 FIGURE 3 is a sectional view taken substantially on line 33 of FIGURE 2; and

' FIGURE 4 is a cross sectional plan view of the flasher of FIGURE 3 taken along the lines 44.

, Referring now to FIGURE 1, a vehicle warning light circuit comprises a battery 19, a group of warning lamps 12, and a flasher 14 connected in circuit therewith to periodically energize the warning lamps 12. One terminal of the battery 10 is connected with a terminal 16 of the flasher 14 while the other terminal of the battery 10 is connected to a second terminal 18 of the flasher as well as to one side of the group of lamps 12 and may comprise a common ground connection. A manually operated switch 20 is interposed between the lamps 12 and the load terminal 22 of the flasher 14.

The first terminal 16 of the flasher has two stationary contacts 24 and 26 associated therewith. The stationary contact 24 has associated therewith a movable contact 28 carried by, an armature 30 spring biased in a direction to tend to separate the contacts. The armature '30, however, ismechanically connected through an arm 32 to a heat expansible wire 34 which is insulated therefrom by a bead 36. The other end of the heat expansible wire 34 is fixed to a stationary point 38 through a second insulating head 40 so that if the wire 34 expands, the armature 30 will move upwardly until the contact 28 thereon engages another stationary contact 42. The armature- 30 is connected through a common circuit 44 in series with a relay coil 46 which in turn is connected to the load terminal 22. The relay coil 46 operates a pair of armatures 48 and 50 which are connected with the common circuit 44. One of the armatures 48 carries a holding contact 52 adapted to cooperate with the stationary contact 26 associated with the first terminal 16, and the other armature 50 carries a contact 54 which cooperates with a stationary contact 56 connected in series with the heat expansible wire 34, a resistor 58, and the second terminal 18. The load terminal 22 of the flasher is directly connected by a shunt circuit 60 to the contact 42 which cooperates with the first armature 30.

' In operation, when the manual switch 20 in the load circuit is open, the contacts will be in those positions shown in FIGURE 1. When the manual switch 20 is closed, current will flow from the battery 10 through the stationary contact 24, the movable contact 28, the first armature 30, the common circuit 44, the relay coil 46, the manual switch 20, the lamps 12, and finally, back to the battery 10 thereby instantly energizing the lamps 12 and energizing the relay coil 46 causing the'two annatures 48 and 50 to move downwardly in engagement with their corresponding stationary contacts 26 and 56. The holding contacts 52, 26 serve to connect the battery 10 to the common circuit 44 so' that the relay coil 46 will remain energized and the lamps 12 will remain lit. The other armature 50 will make contact with contact 56 thereby permitting current from the common circuit 44 to flow through the heat expansible wire 34 and the resistance 58 back to the battery 10 thereby causing the. expansible wire 34 to become heated and to expand. Upon such expansion, the armature 30 breaks contact with the stationary contact 24 and moves upwardly toward the other stationary contact 24. During the period of movement from one stationary contact 28 to the other 42, the holding contact 52 maintains the relay coil 46 and lamps 12 energized. However, when the movablecontact 28 touches the stationary contact 42, the relay coil 46 will be shunted out by the shunt circuit 60 which will be in parallel with the common circuit 44 thereby causing the relay armatures 48 and 50 to drop out and the corresponding contacts 52 and 56 to open. As this occurs, the lamps 12 will be deenergized and, of course, current will cease to flow through the heat expansible wire whereby it will tend to cool and contract. When the heat expansible wire contracts snfficiently, the movable contact 28 on the first armature 30 will be returned to its original position against the stationary contact so that the cycle will be repeated.

It is to be noted that at no time does arcing between any of the contacts occur due to the collapse of the magnetic field of the relay coil. For example, when the movable contact 28 breaks from the stationary contact 24, the common circuit 44 remains energized due to the holding contact 52 and hence there is no callapse of the field and no arcing and, in fact, the movable and stationary contacts 28 and 24 will remain at the same potential. When the movable contact 28 touches the other contact 42, the relay coil .46 will be shortcircuited. As the field collapses, any induced currents in the coil 46 will flow through the shunt circuit 60 and the common circuit 44. When the holding contacts 52 and 26 separate, no arcing will occur because of the discharge path through the shunt circuit 44.

It can readily be seen that small changes of load current will not affect the flashing rate of the flasher 14 since the flashing rate is controlled by the heat expansible wire 34 which is connected directly across the battery 10 so as not to be affected by load current. However, the invention also has the advantage that large changes in load such as that caused by an open filament in one of the loadlamps 12 will decrease the load current tosnch an amount that the relay coil 46 is not sufliciently energized to operate the relay armatures 48, 50. t Then the 3" relay will not operate at all and the failure to operate gives an indication of the condition of the signal lamps by the absence of the usual click associated with the operation of a relay.

While the preferred arrangement of the flasher is that shown in the drawings, itis evident that in a system where the manual switch 20 is connected to terminal 16 rather than to the load terminal 22, the armature 50' may be dispensed with and the expansible wire circuit may be connected directly to the common circuit 44. Since the voltage would be removed from the wire 34 when the switch 20 was opened, the flasher would not operate until the switch 20 was closed.

The structure of the flasher is preferably as illustrated in FIGURES 2, 3 and 4' and includes an insulating base member 62, an envelope 64, three terminals 16, 18, 22 mounted on the base member 62, and the flasher mechanism 14 supported within the envelope 64 by a support member 66 connected to terminal 16. The support 66' is T-shaped and has its upper arms 68 bent at right angles to the main body of the support, and the arms carry the stationary contacts 24,. 26, 56. The relay coil 46 is wound about a core member 70 which is riveted to the support 66 and is insulated therefrom. One end of the coil windingis electrically connected to'the core 70. The relay core70 has near the" bottom thereof a pair of laterally extending pole pieces 72 and has at the top thereof means for carrying'two armatures 30and 4850 which extend downwardly past the pole pieces 72. The armature 48-50 is adapted to be attra'ctedto the pole piece 72 when the relay coil 46 is energized.- The stationary contact 24 serves as astop member for the'first armature 30, and an L-shaped stop member'73 limits the outward movement of the second armature48-50. A tab 74 extending outwardly from the top of the relay'core 70forms a support for the heat eXpansible wire 34 which is insulated therefrom by an insulatingbead 40, and the other end of the'wire 34 is secured to a foot portion of the'first armature 30 through themediurn of a second insulating bead 36. A resistance-wire58 extends from the top of the heat expansiblew'ire 34'toa stationary contact 56. Another L-sha'ped member 76 carried by the support 66 and insulated therefrom has a stationary contact'42 securedthereto. The member 76 is electrically'connected to both-the relay coil 46 and the load terminal 22 and the contact 42 is aligned with the stationary contact 24. The second armature 48-50 carries a pair of contacts 52, 54 aligned with the stationary contacts 26, 56.

It'will'be readily seenthat when the relay coil 46 is actuated, the armature 48-50 will be pulled in to make contact with the stationary contacts26, 56 thereby connecting them in series. Current then will flow from the first terminal 16 through the support member 66 and the closed contacts 24, 28 and-54, 56 to the resistance wire 58 and the heat expansible wire 34 to'the third terminal 18. As the heat expansible wire 34 expands, the first armature 30 will be permitted to move inwardly to make contact with its associated contact 42 which in turn is connected to the load terminal 22 and the lower end of the relay coil winding 46 so that the relay coil will be shunted out inasmuch as the upper portion ofthe armature 30 is connected to the other end of the relay coil winding 46 through the core 70. Accordingly, the relay coil 46 will become deenergized and the second armature 48-50 will be released thereby opening the contacts 52, 26, and

54, 56 and preventing current flow to the heat expansible wire 34. The wire 34 then'contracts to pull the first armature 30 away from the stationary contact 42 and .backtoward the first contact 24 whereupon the cycle indicationof-lamp burn-out will 'be given, that-small variations in the load will not affect the flasher frequency rate; and that the flasher is in normally closed position so that in the event of flasher failure, the load lamps may be energized. g I

The above described embodiments of the invention are intended only as specific illustrations of' the invention and are not to be taken as limiting the scope of the in-' vention which is defined by the following claims:

I claim:

1. A flasher having an input terminal and a load terminal, a relay coil connected with said load terminal, and switch means actuated by the relay coil for alternately connecting said coil to said input terminal and shunting.

out said coil.

2. A flasher having an input terminal and a load terminal, a relay coil connected with said load terminal, and switch means actuated by the relay coil for alter nately connecting said coil to said input terminal and shunting out said coil, said switch means including a double throw switch operated by a heat expansible element.

' 3. A flasher having an input terminal and a load'terminal, a relay coil connected with said load terminal, switch means operated by a heat expansible element for alternately connecting said coil to said input terminal and shunting out said coil, and a relay switchactuated'by the relay coil connecting said element with said input terminay when said coil is energized.

4. A flasher having an input terminal and a load termi-' nal, a relay coil connected with said load terminal, switch means for alternately connecting said coil to said input terminal and shunting out said coil, and a holding switch closed upon energization of said relay to maintain the relay coil energized until it is shunted out by said'switch' means.

5. A flasher having an input terminal and a load terminal, a relay coil connected with said load terminal, switch means for alternately connecting said coil to said input terminal and shunting out said coil, said switch means comprising a double throw switch operated by a heat expansible' element, and relay operated holding switchmeans'to maintain said relay coil energized.

6. A flasher having an input terminal and a load terminal, a relay coil connected with said load terminal, switch means actuated by the relay coil for alternately connecting said coil to said input terminal and shunting out said coil, said switch means including a double throw switch operated by a heat expansible element, relay operated holding switch means to maintain said relay coil e'nergized, and relay operated switch means to connect said heat expansible element with said input terminal.

7. A flasher having an input terminal and a load ter-* load terminal, said switch'means alternately connectable: with each terminal for energizing and shunting out said relay'coil, said relay'switch being connectable with said battery terminal to serve as a holding contact, and means for connecting said heat expansible element to said junctrolled thereby,- a heat expansible element, a switch means tion whereby during energization of said coil theelement expands to move the double throw switch from coil energizing position to coil shunting position.

9. A flasher including a relay coil, a relay switch concontrolled by said element, said switch and switch means eachhavingarnovable Contact Connected to'a cbrrimoii junction, a battery terminal, a load terminal, said relay coil connected between said junction and said load terminal, said switch means alternately connectable With each terminal for energizing and shunting out said relay coil, and the relay switch being connectable with said element whereby during energization of said coil the element expands to move the double throw switch from coil energizing position to coil shunting position.

10. A flasher including a relay coil, two normally open single throw relay switches controlled thereby, a heat expansible element, a double throw switch controlled by said element, said switches each having a movable contact connected to a common junction, a battery terminal, a load terminal, said relay coil connected between said junction and said load terminal, said double throw switch alternately connectable with each terminal for energizing and shunting out said relay coil, one of said relay References Cited by the Examiner UNITED STATES PATENTS 2,788,517 4/1957 Smoot et a1 317-l37 2,992,336 7/1961 Curtner 307132 3,047,773 7/1962 Morton 307132 LLOYD MCCOLLUM, Primary Examiner.

MILTON O. HIRSHFIELD, Examiner. 

10. A FLASHER INCLUDING A RELAY COIL, TWO NORMALLY OPEN SINGLE THROW RELAY SWITCHES CONTROLLED THEREBY, A HEAT EXPANSIBLE ELEMENT, A DOUBLE THROW SWITCH CONTROLLED BY SAID ELEMENT, SAID SWITCHES EACH HAVING A MOVABLE CONTACT CONNECTED TO A COMMON JUNCTION, A BATTERY TERMINAL, A LOAD TERMINAL, SAID RELAY COIL CONNECTED BETWEEN SAID JUNCTION AND SAID LOAD TERMINAL, SAID DOUBLE THROW SWITCH ALTERNATELY CONNECTABLE WITH EACH TERMINAL FOR ENERGIZING AND SHUNTING OUT SAID RELAY COIL, ONE OF SAID RELAY SEITCHES BEING CONNECTABLE WITH SAID BATTERY TERMINAL TO SERVE AS A HOLDING CONTACT, AND THE OTHER OF SAID RELAY 